Tri Power Setup Question
Thread Starter
Intermediate
Joined: Mar 2006
Posts: 36
Likes: 0
From: Brookston IN
Tri Power Setup Question
We are trying to install an rectangular hi perf tri power intake onto oval port heads. 427 - 69 Corvette. Which type of gasket should we use (oval or rectangular)?
We currently have rectangular gaskets, the car starts and idles while cold, but after warming up, the idle goes to 1500 and can not be adjusted down.
All carbs, intake and base plates have been stoned and are not causing any vaccum leaks. We have been chasing this problem for several weeks, any help or experience would be appreciated.
We currently have rectangular gaskets, the car starts and idles while cold, but after warming up, the idle goes to 1500 and can not be adjusted down.
All carbs, intake and base plates have been stoned and are not causing any vaccum leaks. We have been chasing this problem for several weeks, any help or experience would be appreciated.
Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
you are miss matching ports, and your performance will suffer dearly....but if you are intent to do this, then use the sq port gaskets.
Your problems lies with the miss matched ports, either use an oval port intake or sq port heads.
Your problems lies with the miss matched ports, either use an oval port intake or sq port heads.
Thread Starter
Intermediate
Joined: Mar 2006
Posts: 36
Likes: 0
From: Brookston IN
Do you believe this setup will work at all or are we wasting our time?
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
on oval port heads, ran it for awhile tell I could afford the rectangle
port heads, you will just need the rectangle port gaskets.
Last edited by Little Mouse; Jun 16, 2007 at 05:59 PM.
Thread Starter
Intermediate
Joined: Mar 2006
Posts: 36
Likes: 0
From: Brookston IN
We used the rectangular port gaskets, still can't get it to idle. We have been completely through the entire setup three times. Can't get it to idle.
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
Multi-carb setups are notorious for being a pain to properly adjust. The more carbs, the more tinkering is necessary. Have the carbs been rebuilt recently?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
I've never tried this but I'm thinking rec.port gaskets are going to leave leaks.I'm thinking the corners of the rec.ports will be open against the ovals.The Mr Gasket ovals are like a solid gasket with ovals cut in,they should cover the mismatch-I think!!!
Last edited by ...Roger...; Jun 16, 2007 at 11:33 PM.
Melting Slicks
Joined: Feb 2001
Posts: 3,330
Likes: 13
From: Europe , Luxembourg
Hi
Multi-carb setups are notorious for being a pain to properly adjust.
Right, but this does not count for the original Vette tripower setup.
Only the ctr carb has a idle feature, the 2 2ndaries only come in on power. Idle setup is as easy as on a ordinary Holley 4150.
Carb rebuild, choke fully open and nor vacuum leaks and it just works fine.
Günther
Multi-carb setups are notorious for being a pain to properly adjust.
Right, but this does not count for the original Vette tripower setup.
Only the ctr carb has a idle feature, the 2 2ndaries only come in on power. Idle setup is as easy as on a ordinary Holley 4150.
Carb rebuild, choke fully open and nor vacuum leaks and it just works fine.
Günther
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Thread Starter
Intermediate
Joined: Mar 2006
Posts: 36
Likes: 0
From: Brookston IN
The carbs have all been rebuilt, all flat surfaces have been stoned for true-ness.
The choke is hooked up and appears to be working properly.
We are on our 3rd set of intake gaskets, we have tried a few different types. I will have to check to see if we have tried Mr. Gasket Ovals.
What is the exhaust crossover on the intake? We have not blocked off anything.
Thanks for the suggestions guys!!!
The choke is hooked up and appears to be working properly.
We are on our 3rd set of intake gaskets, we have tried a few different types. I will have to check to see if we have tried Mr. Gasket Ovals.
What is the exhaust crossover on the intake? We have not blocked off anything.
Thanks for the suggestions guys!!!
Drifting
Joined: Nov 2002
Posts: 1,692
Likes: 208
From: Loveland, CO
I had your high idle problem. It was not from oval verses rectangular ports, but from the throttle linkage. If the linkage is not adjusted properly, you can get air passage from the end carbs and cause high idle speeds. Be sure your linkage allows the end carbs to close all the way at idle.
Just a suggestion.
Ralph.
Just a suggestion.
Ralph.
Thread Starter
Intermediate
Joined: Mar 2006
Posts: 36
Likes: 0
From: Brookston IN
I had your high idle problem. It was not from oval verses rectangular ports, but from the throttle linkage. If the linkage is not adjusted properly, you can get air passage from the end carbs and cause high idle speeds. Be sure your linkage allows the end carbs to close all the way at idle.
Just a suggestion.
Ralph.
Just a suggestion.
Ralph.
Safety Car
Joined: Oct 1999
Posts: 4,101
Likes: 10
From: NorCal
I had your high idle problem. It was not from oval verses rectangular ports, but from the throttle linkage. If the linkage is not adjusted properly, you can get air passage from the end carbs and cause high idle speeds. Be sure your linkage allows the end carbs to close all the way at idle.
Just a suggestion.
Ralph.
Just a suggestion.
Ralph.
My setup is still not perfect due to a worn out throttle shaft on my primary carb, but I can fix that and it drives well in the mean time. I drive this car daily with no issues. I have a set of LS-7 heads that are going on when I change to a solid cam and improve my exhaust flow. At that point everything will match.
Hans
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Tri-power is great for the street, and not that difficult to keep tuned once they're set up properly. Clears the stock hood, makes good torque, breathes pretty well for top end, and gives surprising economy when you aren't poking on the loud pedal. Only drawbacks are that there's no high-rise version, and there's no cold air set up for it.
If you're putting any rect port intake on oval port heads, you really need to epoxy the ports down and then perform a match, but since an oval port tri-power intake was also produced you'd be going to unnecessary trouble to do so.
If you're putting any rect port intake on oval port heads, you really need to epoxy the ports down and then perform a match, but since an oval port tri-power intake was also produced you'd be going to unnecessary trouble to do so.
Burning Brakes
Joined: Mar 2006
Posts: 915
Likes: 2
From: Lima, OH -- 69 L71 427/435hp
The carbs have all been rebuilt, all flat surfaces have been stoned for true-ness.
The choke is hooked up and appears to be working properly.
We are on our 3rd set of intake gaskets, we have tried a few different types. I will have to check to see if we have tried Mr. Gasket Ovals.
What is the exhaust crossover on the intake? We have not blocked off anything.
Thanks for the suggestions guys!!!
The choke is hooked up and appears to be working properly.
We are on our 3rd set of intake gaskets, we have tried a few different types. I will have to check to see if we have tried Mr. Gasket Ovals.
What is the exhaust crossover on the intake? We have not blocked off anything.
Thanks for the suggestions guys!!!
Some gaskets include restrictors (small square tabs) to block this off, or some gaskets do not have the cutout for the exhaust passover...and if you block it off your choke will not work 'correctly'...it will work, but will take a lot longer to warm up. May want to double check the temp coil is ok, and didn't come unhooked or is bent up.
Safety Car
Joined: Oct 1999
Posts: 4,101
Likes: 10
From: NorCal
Little Mouse, the rec port setup I have on mine was originally purchased used by my brother in law 20 years ago for $200.00 with linkage and air cleaner on my recommendation. He wasn't sure if that was a good deal, but I assured him he would probably be alright. Doh! I bought it from him for $2000.00!
SkunkWorks, the L-68 400hp oval port manifolds are much harder to come by and more expensive (typically) than the 435hp L-71's. There was almost no difference in option prices between the two when new, so 3/4 of the buyers went with the more powerful engine.
Hans
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Tri-power is great for the street, and not that difficult to keep tuned once they're set up properly. Clears the stock hood, makes good torque, breathes pretty well for top end, and gives surprising economy when you aren't poking on the loud pedal. Only drawbacks are that there's no high-rise version, and there's no cold air set up for it.
If you're putting any rect port intake on oval port heads, you really need to epoxy the ports down and then perform a match, but since an oval port tri-power intake was also produced you'd be going to unnecessary trouble to do so.
If you're putting any rect port intake on oval port heads, you really need to epoxy the ports down and then perform a match, but since an oval port tri-power intake was also produced you'd be going to unnecessary trouble to do so.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Thanks, I'll check that out. For guys with taller than standard C3 hoods, that would be the better piece. I assume it came in oval and rect port models.
Racer
Joined: Aug 2003
Posts: 259
Likes: 2
From: Sacramento CA
Check for a vacuum leak at the base of the center carb just in front of the PCV hose. There is a little tab on the base of the 2300. I'm sure you know that that PCV passage is open on the top of the manifold and is sealed by the correct 3X2 base gasket. The wrong gasket there will not correctly cover the passage and it will leak. With the center cark off, it is obvious if you have the wrong gasket on the manifold. I can upload some pictures if you need them.